Flotation of bulk concentrates of molybdenum and copper sulfide minerals and separation thereof



United States Patent 3,426,896 FLOTATION 0F BULK CONCENTRATES 0F MOLYBDENUM AND COPPER SULFIDE MINERALS AND SEPARATION THEREOF Robert E. Baarson, La Grange, and Charles L. Ray, Wheaton, Ill., assignors to Armour Industrial Chemical Company, a corporation of Delaware No Drawing. Filed Aug. 20, 1965, Ser. No. 481,420 U.S. Cl. 209-167 14 Claims Int. Cl. B01d 43/00 ABSTRACT OF THE DISCLOSURE This invention relates to the flotation of bulk concentrates of molybdenum and copper sulfide minerals and separation thereof, and more particularly to the flotation of molybdenum and copper minerals from metallic sulfide ores containing molybdenum, copper and iron minerals and to the subsequent separation of molybdenum minerals from the copper-bearing ores.

An object of the present invention is to provide, in a froth flotation process for the treatment of metallic sulfide ores containing molybdenum, copper and iron minerals, collectors which alone or in synergistic use with common collectors, have better rejection of iron and less affinity for siliceous materials whereby higher recoveries of molybdenum and copper are obtained. Another object is to provide new and improved collectors or combinations of collectors for the recovery of molybdenum and also copper minerals. A further object is to provide a novel process for the separation of molybdenum and copper concentrates in a flotation system. Other specific objects and advantages will appear as the specification proceeds.

In one embodiment of the invention, S-substituted isothiouronium salts are preferably prepared by refluxing an alcoholic solution of thiourea with a fatty halide or with an aromatic halide and are represented by the following formula:

where R is an aliphatic (straight chain or branched chain), cycloaliphatic, or aromatic hydrocarbon group having 2 or more but not more than 24 carbon atoms and preferably not more than 8 carbon atoms, or mixtures thereof, and where X is a halide such as Cl, Br, I, etc. Best results have been obtained when the hydrocarbon group has from 4 to 10 carbon atoms. Other methods of preparation of the collectors may be employed.

The isothiouronium halide compounds thus derived are employed to condition the metallic sulfide pulp together with a frother, if desired, such as methyl amyl alcohol or a polypropylene glycol ether, and following the conditioning, flotation is conducted in the usual manner to effect a bulk concentration and recovery of the molybdenum and copper minerals. As a specific example, a sulfide ore containing copper, iron and molybdenum sulfides is ground to a finely-divided state, and a water pulp of the finely-divided ore is mixed or conditioned with about 0.03 lb. of the collector and about 0.03 lb. of

3,426,896 Patented Feb. 11, 1969 a frother per ton of dry ore. Following conditioning, flotation is conducted for several minutes. An additional amount of collector and frother may then be added and flotation continued for another period. In this illustrative example, the bulk molybdenum and copper concentrates are floated from the iron sulfides and siliceous gangue minerals.

The bulk concentrates obtained as described are then subjected to a process to separate the copper and molybdenum minerals into their respective concentrates. Any of a number of chemical depressant agents may be employed to achieve the subsequent separation of the molybdenum and copper minerals by depressing the copper, such as, for example, Nokes reagents, sodium hydroxide, lime, potassium permanganate, hydrogen peroxide, sodiumsulfide, sodium ferrocyanide, etc. Heat alone is effective in bringing about some depression of the copper minerals. The molybdenum concentrate and copper concentrate may be thereafter subjected to further upgrading operations in order to produce a higher grade of copper or molybdenum concentrate.

In the first flotation operation, the quantities of collector required may range from about 0.005 lb. to about 0.5 lb. per ton of dried ore treated. The required quantities depend upon the nature of the ore treated and upon the particular collector utilized.

Specific examples of the collectors may be designated as benzyl-, ethyl-, isopropyl-, n-butyl-, n-amyl-, isoamyl-, 2-ethylhexyl-, n-octyl-, l-methyloctyl-, dodecyl-, laury1-, tetradecyl-, and tallow isothiouronium chloride, and other satls as defined above where the fatty halide or aromatic halide has from 2 to 24 or, preferably, from 2 to 18 carbon atoms and including mixtures of said halides. The preferred collectors have from 4 to 10 carbon atoms in the collector molecules and include n-butyl isothiouronium chloride, n-amyl isothiouronium chloride, and Z-ethyl hexyl isothiouronium chloride.

Since the collectors are either water-soluble or waterdispersible it is preferred to apply them to flotation as water solutions or water dispersions ranging from about 1% to about 10% active by weight.

We have discovered that when the above-described class of S-substituted isothiouronium salts are used in combination with a known class of collectors which are referred to as sulfhydryl collectors, a better flotation is effected than is achieved by the two types of collectors used separately and their benefits added. Sulfhydryl collectors include the alkyl or aryl dithiophosphates, dithio carbonates (xanthates), dithiocarbamates, thiocarbamates, thioureas, xanthogen formates, mercaptobenzthiazoles, and the like, commonly used for flotation treatment of metallic sulfide ores. Particularly effective synergistic results are obtained by the use of n-butyl isothiouronium chloride or n-amyl isothiouronium chloride or 2-ethylhexyl isothiouronium chloride with such collectors as isopropyl ethyl thionocarbamate or sodium or potassium xanthates having from 2 to 12 carbon atoms. A possible theory in explanation of the synergism of these collectors may be illustrated in connection with n-butyl isothiouronium chloride. The n-butyl isothiouronium chloride ionizes with a positive charge and can combine with the sulphur atom of copper sulfide mineral, while the negatively-charged portion of the isopropyl ethyl thionocarbamate normally combines with the copper atom. Either of these collectors can complex with the individual copper or sulfur atoms. It is possible that the synergistic effect is caused by a filling in the voids on the surface coating that may be left by the use of one of these compounds alone.

The isothiouronium salts have been discovered to be particularly effective in floating molybdenum concentrates while also floating copper concentrates therewith. In combination with the common reagents, such as isopropyl ethyl thionocarbamate or sodium isopropyl xanthate, etc., we prefer to employ isothiouronium chloride collector in combination with such common collector r.p.m.), conditioned for 30 seconds (60 seconds if the collector was added to the flotation cell) with Dowfroth 250 and floated minutes.

An additional flotation step, preceded by a collector addition and conditioning in the cell, was made for 3 in the proportions of 1:1 to 5: 1. Best results have been ob- 5 minutes. The two rougher concentrates were combined tained when the proportion of 4:1 is employed. It will be and thickened. The thickened bulk concentrate was understood that such proportions may be varied widely then reground in a ball mill for 5 minutes at approxdepending upon the character of the ores being treated. imately 4550% solids. A minimum pH level of 11.9 In the second stage in which the concentrates are was used in a cleaner flotation step. The reground pulps separated, we have discovered that among depressants were diluted to about 20% solids in a 250 gram stainless which may be employed, sodium ferrocyanide is unusualsteel Denver flotation cell (1200 r.p.m.) conditioned ly effective as a depressant and when used with the colseconds (1 minute, if additional collector was added to lectors permits greater filterability of the molybdenum the cell) and floated 3 minutes, constituting the first and also the copper concentrates, compared with the use 15 cleaner flotation step. A second cleaner flotation product of such depressants as Nokes reagents, which are diswas collected for 2 minutes after another 15 seconds persants. The filtration is accomplished in less time and conditioning period. The two cleaner products were comwith less use of separating equipment. In the second bined and assayed for metal content. Test results are set stage in which the depressant is added, it is common to out in Table II. add a small amount of collector at the same time that the depressant is added. By the use of ferrocyanide, it TABLE H is found that less collector need be added, while at the Percent Recovery same time greater filterability of the molybdenum con- Bulk centrates, etc. iS obtained. Reagent #l'l Rougher Cleaner The invention may be further illustrated by the following examples and discussion, which are illustrative of Mo Cu Mo Cu preferred embodiments of the invention, but the inven- M6 tion is not limited thereby.

D0wZ-11 0.02 75.1 91.2 68.1 856 Example I 2-ethylhcxyl lsothiouronlum chloride-.. 0.08 95.9 94.4 88.7 81 0 n-Alnyl Isothrouronium chloride 0.08 93.6 93.0 88.9 69 1 Dow Z-200 0.03 Following the procedure described above, a copperand nnnnnnnnn nnnnn nnnnnnnnn nnnnn nnn 99.99198939922 929 ???;111;; 99 .9..9:-.=r-.s- %..91 treated using the collector agents described in the followand ing Table I at a PH level between 11 and 1L5I and with n-Butyllsothiouronlum chloride 0.04 91.4 92.4 88.1 88.4 the results there shown.

TABLE I Analysis of Products Concentrate Tails Percent Test Collector #IT Recovery Percent Percent Percent Percent Cu Mo Cu Mo Cu M0 485-205.- {:%g9:::::::::::::::'"" 3 16.61 4.16 0.071 0.0658 97.8 92.4 485-95 n-Dodeeylisothiouronium Cl 0.10 15.82 3.60 0.100 0.0567 97.1 93.0 485-97 n-Octylisothiouronium Cl... 15.78 3.45 0.098 0.0485 97.0 93.4 485-99- ZethylhexylisothlouroniumC 19.30 4.49 0.091 0.0570 97.2 92.8 485-103 n-Amylisothiouronium o1 0.10 18.43 3.89 0.083 0.0594 97.7 92.5 485235 Isopropylisothiouronium C1 0.12 20.07 4.29 0.086 0.0998 97.5 88.2 485237 0.12 21.37 4.39 0.268 0.186 92.5 78.5

Ethyl isothiouronium Cl Z-200 is a designation for isopropyl thionocarbamate, and Z-11 is a desgination for sodium isopropyl xanthate. This combination of these collectors is considered standard for the type of ore tested.

From Table I, it can be seen that good recovery of copper and molybdenum minerals is produced by the use of the collectors of the invention. It is also illustrated that the number of carbon atoms and the arrangement of these carbon atoms in the hydrocarbon group has influence on the so-called collecting power of the collector on a particular ore.

Example II A South American ore (2.85% Cu and 0.7% Moconsidered a high grade ore) was crushed and ground ttor 12 minutes in a laboratory rod mill to a mesh of grind containing 20.3% 'by weight of plus 65 mesh size particles and 30.0% by weight of minus 200 mesh size particles.

Grind was at solids and the amount of collector added to the mill varied with the collectors tested. The bulk flotation pH level varied between 11.3 and 11.7. The ground pulps were diluted to about 20% solids in a 1,000 gram stainless steel Denver flotation cell of (1800 In the above Table I,

Table II illustrates that the combined use of alkylisothiouronium chloride with a sulfhydryl collector, such as Z-200, provides a synergistic improvement in the recovery of molybdenum and copper when compared to the use of the alkylisothiouronium collector used alone or with a collector system considered standard for the ore tested.

The Z-200 is a collector which is normally classed as an anionic collector (exhibiting a negative charge) while the alkylisothiouronium chloride is a cationic collector which ionizes with a positive charge. Two such reagents would normally be considered chemically incompatible and yet compatibility in the process is illustrated in the above data.

Example 111 A low .grade Cu-Mo ore from a mining company in the Southwestern United States was crushed to minus 10 mesh and ground with lime in a laboratory rod mill. The ground feed to flotation contained 5.1% by weight of plus 65 mesh particles and 49.4% by weight of minus 200 mesh particles.

After grinding, the pulp was transferred to a Denver laboratory flotation machine, diluted to proper pulp density and the pH adjusted to that required, if necessary.

Collectors and frothers were added to the cell and the pulp conditioned 2 minutes. After a. 2-minute float, a second increment of reagents was added and the pul reconditioned and refioated. The separate froths were dried, weighed, and assayed.

the three stages, to the same total consumption as in the tests using the dithiophosp'hate collector.

Table IV illustrates an advantage in the use of aryl or alkyl isothiouronium ohloride compounds for the recovery of molybdenum and copper minerals.

TABLE III Assay Recovery- Collector #/T Rougher Conc. Rougher Tail Rougher Percent Percent Percent Percent Percent Percent Mo u Mo Cu Mo Cu 011621 8mple #1; (0.45% Cu and 0.02%

o Potassium amyl xanthate 0. 10 0. 227 5. 8 0. 0077 0. 084 65. 5 82. n-Amyl isothiouronium chloride 0 10 0. 195 5.6 0.0071 0. 080 66. 7 83. 6 Potassium amylranthate 0.04

an n-Amyl isothiouronium chloride..- 0 04 0.172 4.2 0.0057 0.084 74.7 82. 7 Range oil 0a 0.04

an Potassium amyl xanthate 0.06 0. 240 6. 4 0.007 0.203 66. 0 66. 9 011Ti ample #2; (0.7% Cu and 0.32%

o n-Amyl isothiouronium chloride..- 0 07 0.268 7.4 0.014 0.156 79.0 55.6 Potassium amylranthate 0. 06

an n-Amyl isothiouronium chloride..- 0 04 0.366 8.1 0.009 0.155 79.5 75.0 Range 011 0.04

and Potassium amyl xanthate 0.06 0. 329 8. 2 0. 010 0.132 68. 81. 2

Table III illustrates an advantage in the use of alkyl- Example V isothiouronium chloride reagents alone or in combination with other promoters such as potassium 'amyl xanthate to provide improved recovery of molybdenum and copper.

Example IV A low grade Cu-Mo ore (0.81% Cu and 0.008% Mo) from Southwestern United States was crushed to minus 10 mesh, and was mixed and split samples. These were ground in a laboratory rod mill with enough lime to give the desired pH to the diluted pulp. The ground ore contained an average of 0.7% by weight of plus 65 mesh particles and 59.5% by weight of minus 200 mesh particles.

In a standard reference test, sodium di-ethyl dithiophosphate was added to the grinding mill and the diluted pulp floated 5 minutes in a Denver flotation machine. In

down to 500 gram test additional tests, the isothiouronium chlorides were added to the diluted pulp, conditioned in the machine and floated in three stages of three minutes each. Collector addition using the isothiouronium chlorides was 0.005 lb./T, 0.01 lb./T and 0.01 1b./T respectively in Bulk cleaner concentrates of copper and molybdenum were obtained as described in Example I'I, dewatered, and were subjected to a flotation process for the separation of molybdenum minerals from copper minerals using various depressing agents for copper minerals in accordance with the following procedure.

The thickened copperamolybdenum bulk cleaner concentrate was subjected to the particular depressant system being tested by conditioning in a stainless steel beaker with an air-driven mixer. The conditioned pulps were then diluted in a 250 gram stainless steel Denver flotation cell (1200 r.p.m.), pH adjusted to 7.0-7.3 (except when the sodium sulfide depressant system was used, in which case the pH level was near 12.0), conditioned for 2 minutes and floated 4 minutes.

The rougher Mo concentrate thus obtained was then subjected to a second addition of the depressant system being tested. The conditioned pulp was then diluted to flotation density in a 250 gram stainless steel Denver flotation cell (1000 r.p.rn.), pH adjusted to 7.0-7.3, conditione for 1 minute and floated for 3 minutes.

Test results are shown in Table V.

TABLE V #/T Percent Recovery #IT Mo Concentrate I Reagent Original Bulk Rougher Bulk Cleaner Depressant Feed to Percent Grade Feed Mo Re- Cu Mo Cu Circuit covery, Percent Percent Mo 0 Cu Dow Z-200 .3. 0.06

an Dow Z-ll 0.02 75. 1 91. 2 68. I 85.6 Nokes' LR 744 1.5 25. 1 38. 4 2.5 n-Amyl isothiouronium chloride 0.08 91. 5 91. 5 79.2 64.3 Nokes LR 744.... 1.5 44. 6 41.9 1.7 Z-ethylhexyl isothiouronium ehloride 0.08 94.4 95.9 88.7 81.0 Nokes LR744 3. 5 38. 5 41. 1 1.3 Dow Z-200 -21. 0. 03

an nAmyl isothiouronium chloride 0.05 91.3 92.7 79.6 87.8 Nokes LR 744 0.95 48.5 38.6 2.3 2'ethylhexyl isothiouronium chloride 0.08 95. 5 93.3 90.8 76.3 Sodium ierrocyanide. 6.4 73.7 32. 5 1.8 n-Amyl isothiouronium chloride" 0.08 94.1 92. 2 89. 2 67.1 Sodium ierroeyanide. 5.0 78.8 30.7 1.7 Dow Z-200 0. 03

and n-Amyl isothiouronium chloride 0. 05 Dow Z-200 0. 03

and n-Butyl isothiouronium chloride.. 0.04 Dow 2-200 0. 03

and n-Butyl isothiouronium chloride. 0. 04 Dow Z-200 .3. 03

an n-Amyl isothiouronium chloride 0. 05 94.4 93.0 88. 2 .6 Potassium perman- 6. 4 72.3 34. 4

. game e.

Table V illustrates the advantage of using alkylisothiouronium chloride reagents, alone or in combination with other reagents for recovery of copper and particularly molybdenum, utilizing Nokes LR 744 depressant for separation of molyzdenum minerals and copper minerals from bulk concentrates.

Table V also illustrates the effectiveness of alkylisothiouronium compounds, alone or in combination with other reagents, utilizing depressants such as sodium ferrocyanide, sodium sulfide, or potassium permanganate. It can be seen that the alkylisothiouronium reagents, when used with the sodium ferrocyanide, show much improved recovery of molybdenum over recoveries obtained when Nokes LR 744 reagent was used, while at the same time greater filterability of the molybdenum concentrates and also of the copper concentrates was obtained, the filtering operation being accomplished in much less time compared for instance to the results obtained with Nokes LR 744 reagent which is by nature a dispersing agent.

While in the foregoing specification we have set forth specific procedure in considerable detail for the purpose of illustrating embodiments of the invention, it will be understood that such details of procedure may be varied widely by those skilled in the art without departing from the spirit of our invention.

We claim:

1. In a process for the separation of metallic ores containing molybdenum, copper and iron minerals, the steps of conditioning a water suspension of such ores in finely-divided condition with a collector comprising an S-substituted isothiouronium salt having the structure where R is an aliphatic, cycloailiphatic or aromatic hydrocarbon having 2 to 24 carbon atoms and where X is a halide, introducing a frothing agent and air to float the molybdenum and copper concentrates away from said iron, and subsequently depressing the copper to recover the molybdenum concentrate.

2. The process of claim 1 in which sodium ferrocyanide is introduced to depress the copper concentrate.

3. The process of claim 1, in which the hydrocarbon has from 4 to carbon atoms.

4. The process of claim 3 chloride.

5. The process of claim 1 in which the salt is n-butyl isothiouronium chloride.

6. The process of claim isothiouronium chloride.

7. The process of claim 1 in which the salt is 2-ethylhexyl isothiouronium chloride.

in which the halide is 1 in which the salt is n-amyl- 8. In a process for the separation of metallic sulfide ores containing molybdenum, copper and iron minerals, the steps of conditioning a water suspension of such ores in finely-divided condition with a collector comprising an S-substituted isothiouronium salt having the structure where R is an aliphatic, cycloaliphatic or aromatic hydrocar-bon having from 2 to 24 carbon atoms, and where X is a halide, in combination with a reagent selected from the group consisting of isopropyl ethyl thionocarbamate, sodium alkyl xanthate having from 2 to 12 carbon atoms, potassium alkyl xanthate having from 2 to 12 carbon atoms, alkyl dithiophosphates, aryl dithiophosphates, and mercaptobenzthiazoles, introducing a frothing agent and air to float the molybdenum and copper concentrates away from said iron, and subsequently depressing the copper to recover the molybdenum concentrate.

9. In a process for the separation of metallic sulfide ores containing molybdenum, copper and iron minerals, the steps of conditioning a water suspension of such ores in finely-divided condition with a collector selected from the group consisting of n-butyl isothiouronium chloride, n-amyl isothiouronium chloride, and Z-ethylhexyl isothiouronium chloride, with isopropyl ethyl thionocarbamate, introducing a frothing agent and air to float the molybdenum and copper concentrates away from said iron, and subsequently depressing the copper to recover the molybdenum concentrate.

10. In a process for the separation of metallic sulfide ores containing molybdenum, copper and iron minerals, the steps of conditioning a water suspension of such ores in finely-divided condition with a collector selected from the group consisting of n-butyl isothiouronium chloride, n-amyl isothiouronium chloride, and Z-ethylhexyl isothiouronium chloride, with sodium isopropyl xanthate, introducing a frothing agent and air to float the molybdenum and copper concentrates away from said iron, and subsequently depressing the copper to recover the molybdenum concentrate.

11. In a process for the separation of metallic sulfide ores containing molybdenum, copper and iron minerals, the steps of conditioning a water suspension of such ores in finely-divided condition with n-butyl isothiouronium chloride and isopropyl ethyl thionocarbamate, introducing a frothing agent and air to float the molybdenum and copper concentrates away from said iron, and subsequently depressing the copper to recover the molybdenum concentrate.

12. In a process for the separation of metallic sulfide ores containing molybdenum, copper and iron minerals,

the steps of conditioning a water suspension of such ores in finely-divided condition with n-butyl isothiouronium chloride and isopropyl ethyl thionocarbamate, adding a frothing agent and air to float molybdenum and copper concentrates from iron sulfide and depressing the copper concentrate from the molybdenum concentrate by the addition of sodium ferrocyanide.

13. In a process for the separation of metallic sulfide ores containing molybdenum, copper and iron minerals, the steps of conditioning a water suspension of such ores in finely-divided condition with n-butyl isothiouronium chloride and sodium isopropyl xanthate, introducing a frothing agent and air to float the molybdenum and copper concentrates away from said iron, and subsequently depressing the copper to recover the molybdenum concentrate.

14. In a process for the separation of metallic sulfide ores, the steps of conditioning a Water suspension of such ores in finely-divided condition with n-butyl iso- References Cited UNITED STATES PATENTS 1,950,537 3/1934 Barthelemy 209-167 2,664,199 12/1953 Barker 209l67 2,336,868 12/1943 Jayne 209-166 2,691,635 10/1954 Harris 25261 3,093,666 6/1963 Du Brow 25261 X FRANK W. LUTTER, Primary Examiner. ROBERT HALPER, Assistant Examiner. 

